In order to examine the dependence of ITO(Indium Tin Oxide) thin films on wavelengths of laser at ablation, the first, second, third and fourth harmonic of diode-pumped Nd:YLF laser were employed respectively. Patterning was performed successfully at any wavelength. The laser fluence was controlled by defocusing of beam. We made comparisons with each fluence for ablating ITO layer on substrate glass, and observed surface of the glass and edge of groove formed by laser etching. Near the groove, much debris was deposited. So we examined the effects of various sealed gases having molecular weight (e.g. He, N2, Ar). The amount of debris was reduced by only He gas. Additionally we measured index of absorption by ITO and substrate glass for lights. The range for wavelengths was swept from ultraviolet to infrared. In conclusion, we recognized that the removal of ITO was more efficient with increase of absorption of lights.